Rotary forming drums and the process they are used in are not new to the art. As described in U.S. Pat. No. 6,086,800 issued to Manlove on Jun. 11, 2000 there is a Flat Bed Thermoforming process which is further noted by the citation of U.S. Pat. Nos. 3,470,281, 3,578,735, and 3,600,753 therein. Other United States Patents that disclose thermoforming processes using rotary forming drums include U.S. Pat. Nos. 6,814,905, 6,976,835 and 6,394,783.
However, all of these prior art patents fail to disclose a rotary forming drum that has the clear advantages of the instant invention. The novel vacuum distribution and control system of the instant invention allows for rapid induction of molten thermoplastic into the trays of the rotary forming drum. After the vacuum phase is completed the articles of the tray cool proceed along the drum. As they near their exit point the novel trays of the rotary forming drum pivot outward via the cam follower activating the cam roller. The trays move outward, forcing the formed articles from the trays cleanly and efficiently. The trays then are returned to their original position via a set of internal and external return springs. It should be noted that the trays of this invention contain cavities i.e. female molds, as opposed to the projections, i.e. male molds of the prior art.